Process for the preparation of phosphosulfide compounds useful as oil lubricants

ABSTRACT

Useful as additive for lubricating oils are novel phosphosulphur compounds in accordance with the general formula (I): 
     
         (((R.sup.1 --S.sub.x --O.sub.y --A--).sub.r B.sub.v).sub.p P(X)--Y.sub.i 
    
      --) q  Z m   
     in which e.g. R 1  represents an alkyl or alkenyl group, A represents the group --(CH 2 ) n  --O--, B represents the group --P(S)--S--CH 2  --(CH 3 )--O--, X represents an oxygen atom or a sulphur atom, Y represents an oxygen atom, a sulphur atom or an oxygen or sulphur-containing hydrocarbon chain, Z represents a hydrogen, chlorine or sulphur atom, a polysulphide chain, a metal or an alkyl or alkenyl group, x=1,2 or 3, y=0, 1 or 2, v is 0 or 1, r is 1 (if v=0) or r=2 (if v=1), p=2 or 3, t=0 or 1, m=0,1 or 2, q=the valency of Z if Z is a metal or q=1 or 2 and n is an integer from 1 to 30.

This application is a continuation of application Ser. No. 07/749,783,filed Aug. 26, 1991 now U.S. Pat. No. 5,306,436.

BACKGROUND OF THE INVENTION

The present invention relates to novel phosphosulphur compounds (i.e.sulphur and phosphor-containing) and their use as petroleum additives,particularly as antioxidant, antiwear, extreme-pressure andanticorrosive additives for lubricating oils.

Antiwear and extreme-pressure additives have been used for decadesparticularly in engine oils, transmission fluids and hydraulic fluids.Numerous additive types have been developed and several of them havemade it possible to very significantly reduce deterioration tomechanisms and therefore extend their life.

Among the antiwear and extreme-pressure additives the most active andtherefore the most significantly industrially developed have beendialkyl and diaryl dithiophosphates and metallic dialkyldithiocarbamates, (particularly those of zinc), alkyl thiophosphates,tricresyl phosphate, didodecyl phosphate, sulphurized terpenes,sulphur-containing spermaceti oil and various chlorine compounds.Certain of them are described in U.S. Pat. Nos. 2,364,283, 2,364,284,2,365,938, 2,410,650, 2,438,876, 3,190,833. These are generallycompounds containing heteroatoms such as sulphur and phosphorus, eitheralone (e.g. tricresyl phosphate, sulphur-containing terpenes anddithiocarbamates) or in combination (e.g. metallic dialkyldithiophosphates and alkyl thiophosphates). Reference can be made toFrench Patents FR-A-982 719 and 1 321 821 and U.S. Pat. Nos. 2,750,342and 3,944,495.

The phosphosulphur compounds used previously have relative sulphur andphosphorus quantities which are imposed by the stoichiometry of thereactions during their synthesis and which in particular give themantiwear and extreme-pressure properties, which cannot be modified bythe Expert.

SUMMARY OF THE INVENTION

Novel phosphosulphur compounds have now been discovered, which can beused as lubricating additives, preferably prepared by the reaction ofconventional phosphor-containing reagents with (poly)sulphurizedalcohols, which makes it possible to modify at random the relativeantiwear and extreme-pressure performances of said phosphosulphurcompounds.

The phosphosulphur compounds according to the invention are inaccordance with the general formula (I):

    (((R.sup.1 --S.sub.x --O.sub.y --A--).sub.r B.sub.v --).sub.p P(X)--Y.sub.t --).sub.q Z.sub.m

in which R¹ represents an alkyl group (e.g. methyl, ethyl or tert.butyl) or alkenyl group (e.g. CH₂ ═C(CH₃)--CH₂ --), which may or may notbe functionalized, containing 1 to 30 carbon atoms; A represents thegroup --(CH₂)_(n) --O-- or the group ##STR1## in which n is an integerfrom 1 to 30 and R² and R³, which can be the same or different, eachrepresent a hydrogen atom or a substantially hydrocarbonated monovalentradical with 1 to 30 carbon atoms (e.g. methyl, ethyl, etc.), R² and R³can be interlinked to form a polymethylene chain and in general Arepresents the group --(CH₂)_(n) --O--; B represents the group ##STR2##in which R⁴ and R⁵, which can be the same or different, in each caserepresent a hydrogen atom or a substantially hydrocarbonated monovalentradical with 1 to 30 carbon atoms and R⁴ and R⁵ can be interlinked toform a polymethylene chain; e.g. R⁴ =H and R⁵ =H or CH₃ ; X representsan oxygen atom or a sulphur atom; Y represents an oxygen atom, a sulphuratom or a sulphur or oxygen-containing hydrocarbon chain; Z represents ahydrogen atom, a chlorine atom, a sulphur atom, a polysulphurized chain,a metal chosen e.g. from among the group formed by sodium, zinc, copper,molybdenum, lead, antimony and cadmium, an oxygen or sulphur-containingderivative of molydbenum or an alkyl, alkenyl or R⁶ group, which may ormay not be functionalized, containing 1 to 30 carbon atoms; x is aninteger equal to or greater than 1 and preferably equal to 1,2 or 3: yis equal to 0,1 or 2 and if y=0 then (R¹ --S_(x) --O_(y) --A--)_(r) iswritten (R¹ --S_(x) --A--)_(r) ; v is equal to 0 or 1 (if v=0 there isthen no B group in the formula of compounds according to the invention);r is equal to 1 if v=0 and r is equal to 2 if v=1; p is equal to 2 or 3;t is equal to 0 or 1 (if t=0 then there is no Y group in the formula ofcompounds according to the invention); m is equal to 0 or 1 (if m=0 thenthere is no Z group in the formula of compounds according to theinvention); and q is an integer equal to the valency of Z if Z is ametal or a number equal to 1 or 2.

In the definition of R¹ and R⁶, the term functionalized group isunderstood to mean a group containing at least one heteroatom such ase.g. chlorine or sulphur, or at least one chemical function e.g. chosenfrom among the carboxylic, aldehyde, ketone, nitrile, hydroxyl andepoxide functions, whereby several of these functions can be present inthe same R¹ and R⁶ group.

The different types of phosphosulphur compounds according to theinvention are preferably as follows (the term (poly)sulphurized meansthat the compound is either monosulphurized (x=1) or polysulphurized(x>1)):

polysulphurized dialkyl dithiophosphoric and dialkenyl dithiophosphoricacids of general formula (II):

    (R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(S)--SH --SH

i.e. of general formula (I) in which A=--(CH₂)_(n) --O, X=S, Y=S, Z=H,y=0, v=0, r=1, p=2, t=1, q=1 and m=1; morevover in formula (II) x is anumber equal to or greater than 2 and as examples of compounds offormula (II) reference can be made to those for which R¹ =tert. butyl,x=2, n=2,3,4,5 or 6 and preferably n=2,3 or 6 and R¹ =CH₂ ═C(CH₃)--CH₂--, x=2, n=2,3,4,5 or 6 and preferably n=3;

(poly)sulphurized alcohols of general formula (III): ##STR3## in whichR⁷ and R⁸, which can be the same or different, in each case represent ahydrogen atom or a substantially hydrocarbon-containing monovalentradical with 1 to 30 carbon atoms and R⁷ and R⁸ can be interlinked toform a polymethylene chain; formula (III) corresponding to generalformula (I) in which A=--(CH₂)_(n) --O, X=S, Y=S, ##STR4## y=0, v=0,r=1, p=2, t=1, q=1, m=1; moreover, in formula (III), x is a number equalto or greater than 1; examples of compounds of formula (III) being thosefor which R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x--1 or 2, n=2,3,4,5or 6, R⁷ =H and R⁸ =H or CH₃ ; the polysulphurized metal salts ofgeneral formula (IV):

    ((R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(S)--S--).sub.q Z

in which Z is a metal and q is a number equal to the valency of Z, i.e.of general formula (I) in which A=--(CH₂)_(n) --O--, X=S, Y=S, Z is ametal (e.g. zinc) y=0, v=0, r=1, p=2, t=1, q=valency of Z and m=1;moreover, in formula (IV), x is a number equal to or greater than 2,e.g. examples of compounds of formula (IV) are those for which R=tert.butyl or CH₂ ═C(CH₃)--CH₂ --, x=2, n=2,3,4,5 or 6, Z=Zn and q=2;

(poly)sulphurized dihydrocarbyldithiophosphyldithiophosphoric acids andcorresponding poly(sulphurized) metal salts of general formula (V):##STR5## in which Z=H or a metal (e.g. zinc), i.e. of general formula(I) in which A=--(CH₂)_(n) --O--, X=S, Y=S, Z=H or a metal, y=0, v=1,r=2, p=2, t=1, q=1 (if Z=H) or q is the valency of Z (if Z is a metal)and m=1; moreover, in formula (V), x is a number equal to or greaterthan 1; examples of compounds of formula (V) being those for which R¹=tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2, n=2,3,4,5 or 6, R⁴ =H, R⁵=H or CH₃, Z=Zn (and q=2) or Z=H (and q=1);

(poly)sulphurized organic compounds of general formula (VI):

    (R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(S)--S--R.sup.6

i.e. of general formula (I) in which A=--(CH₂)_(n) --O--, X=S, Y=S,Z=R⁶, y=0, v=0, r=1, p=2, t=1, q=1 and m=1; moreover, in formula (VI), xis a number equal to or greater than 1 and R⁶ is the monovalent radicalof an alcohol R⁶ --OH; examples of compounds of formula (VI) are thosefor which R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2, n=2,3,4,5 or6 and R⁶ =(CH₃)₃ --C--S--(CH₂)₃ --CH₂ --;

(poly)sulphurized organic compounds of general formula (VII): ##STR6##i.e. of general formula (I), in which A=--(CH₂)_(n) --O--, X=S, Y=S,Z=R⁶, y=0, v=1, r=2, p=2, t=1, q=1 and m=1; moreover, in formula (VII),x is a number equal to or greater than 1; examples of compounds offormula (VII) being those for which R=tert. butyl or CH₂ ═C(CH₃)--CH₂--, x=1 or 2, n=2,3,4,5 or 6, R⁴ =H, R⁵ =H or CH₃ and R⁶ =(CH₃)₃--C--S--(CH₂)₃ --CH₂ --;

polysulphurized dialkylphosphoric and dialkenylphosphoric acids and thecorresponding polysulphurized metal salts of general formula (VIII):

    ((R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(O)--O--).sub.q Z

in which Z=H or a metal (e.g. zinc), i.e. of general formula (I), inwhich A=--(CH₂)_(n) --O--, X=O, Y=O, Z=H or a metal, y=0, v=0, r=1, p=2,t=1, q=1 (if Z=H) or q is the valency of Z (if Z is a metal) and m=1;moreover, in formula (VIII) x is a number equal to or greater than 2 andexamples of compounds of formula (VII) are those for which R¹ =tert.butyl or CH₂ --C(CH₃)--CH₂ --, x=2, n=2,3,4,5 or 6, Z=Zn (and q=2) orZ=H (and q=1);

(poly)sulphurized dihydrocarbyldithiophosphylphosphoric acids and thecorresponding (poly)sulphurized metal salts of general formula (IX):##STR7## in which Z=H or a metal (e.g. zinc), i.e. of general formula(I) in which A=--(CH₂)_(n) --O--, X=O, Y=O, Z=H or a metal, y=0, v=1,r=2, p=2, t=1, q=1 (if Z=H) or q is the valency of Z (if Z is a metal)and m=1; moreover, in formula (IX), x is a number equal to or greaterthan 1; examples of compounds of formula (IX) are those for which R¹=tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1, n=2,3,4,5 or 6, R⁴ =H, R⁵ =Hor CH₃, Z=Zn (and q=2) or Z=H (and q=1);

polysulphurized dialkylchlorophosphates and dialkenylchlorophosphates ofgeneral formula (X):

    (R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(O)--Cl

i.e. of general formula (I) in which A=--(CH₂)_(n) --O--, X=O, Z=Cl,y=0, v=0, r=1, p=2, t=0, q=1 and m=1; moreover, in formula (X), x is anumber equal to or greater than 2; examples of compounds of formula (X)being those for which R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=2,n=2,3,4,5 or 6 and preferably n=3 or 6;

(poly)sulphurized dialkylchlorothiophosphates anddialkenylchlorothiophosphates of general formula (XI):

    (R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(S)--Cl

i.e. of general formula (I) in which A=--(CH₂)_(n) --O--, X=S, Z=Cl,y=0, v=0, r=1, p=2, t=0, q=1 and m=1; moreover, in formula (XI), x is anumber equal to or greater than 1; examples of compounds of formula (XI)being those for which R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2,n=2,3,5 or 6 and preferably n=3 or 6;

(poly)sulphurized organic compounds of general formula (XII): ##STR8##i.e. of formula (I) in which A=--(CH₂)_(n) --O--, X=O, Z=Cl, y=0, v=1,r=2, p=2, t=0, q=1 and m=1; moreover, in formula (XII), x is a numberequal to or greater than 1; examples of compounds of formula (XII) beingthose for which R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2,n=2,3,4,5 or 6, R⁴ =H and R⁵ =H or CH₃ ;

(poly)sulphurized organic compounds of general formula (XIII): ##STR9##i.e. of formula (I) in which A=--(CH₂)_(n) --O--, X=S, Z=Cl, y=0, v=1,r=2, p=2, t=0, q=1 and m=1; moreover, in formula (XIII), x is a numberequal to or greater than 1; examples of compounds of formula (XIII)being those for which R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2,n=2,3,4,5 or 6, R⁴ =H and R⁵ =H or CH₃ ;

(poly)sulphurized trialkylphosphates and trialkenylphosphates of generalformula (XIV):

    (R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.3 P(O)

in which x is a number equal to or greater than 1, i.e. of generalformula (I) in which A=--(CH₂)_(n) --O--, X=O, y=0, v=0, r=1, p=3, t=0,q=1 and m=0; examples of compounds of formula (XIV) being those forwhich R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2 and n=2,3,4,5 or6;

(poly)sulphurized organic compounds of general formula (XV): ##STR10##in which x is a number equal to or greater than 1, i.e. of formula (I)in which A=--(CH₂)_(n) --O--, x=0, y=0, v=1, r=2, p=3, t=0, q=1 and m=0;examples of compounds of formula (XV) being those for which R¹ =tert.butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2, n=2,3,4,5 or 6, R⁴ =H and R⁵ =Hor CH₃ ;

(poly)sulphurized trialkyl thiophosphates or trialkenyl thiophosphatesof general formula (XVI):

    (R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.3 P(S)

in which x is a number equal to or greater than 1, i.e. of generalformula (I) in which A=--(CH₂)_(n) --O--, X=S, y=0, v=0, r=1, p=3, t=0,q=1 and m=0; and examples of compounds of formula (XVI) are those forwhich R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2 and n=2,3,4,5 or6;

(poly)sulphurized organic compounds of general formula (XVII): ##STR11##in which x is a number equal to or greater than 1, i.e. of formula (I)in which A=--(CH₂)_(n) --O--, X=S, y=0, v=1, r=2, p=3, t=0, q=1 and m=0;examples of compounds of formula (XVII) are those for which R¹ =tert.butyl or CH₂ ═C(CH₃)--CH₂, x=1 or 2, n=2,3,4,5 or 6, R⁴ =H and R⁵ =H orCH₃ ;

(poly)sulphurized dialkyl phosphonates or dialkenylphosphonates ofgeneral formula (XVIII):

    (R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(O)--H

in which x is a number equal to or greater than 1, i.e. of generalformula (I) in which A=--(CH₂)_(n) --O--, X=O, Z=H, y=0, v=0, r=1, p=2,t=0, q=1 and m=1; and examples of compounds of formula (XVIII) are thosefor which R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2, n=2,3,4,5 or6;

(poly)sulphurized organic compounds of general formula (XIX): ##STR12##in which x is a number equal to or greater than 1, i.e. of generalformula (I) in which A=--(CH₂)_(n) --O--, X=O, Z=H, y=0, v=1, r=2, p=2,t=0, q=1 and m=1; and examples of compounds of formula (XIX) are thosefor which R¹ =tert. butyl or CH₂ ═C(CH₃)--CH₂ --, x=1 or 2, n=2,3,4,5 or6, R⁴ =H and R⁵ =H or CH₃ ;

and (poly)sulphurized organic compounds of general formula (XX):##STR13## in which x is a number equal to or greater than 1 and n is anumber equal to or greater than 3, i.e. of general formula (I) in whichA=--(CH₂)_(n) --O--, X=S, ##STR14## R⁷ and R⁸ being defined ashereinbefore, Z=S_(w), w being a number equal to or greater than 1, y=0,v=0, r=1, p=2, t=1, q=1 and m=1; and examples of compounds of formula(XX) are those for which R¹ =CH₃, C₂ H₅ --, (CH₃)₃ C-- and CH₂═C(CH₃)--CH₂, x=1,2 or 3, n=3,4,5 or 6, R⁷ =H, R⁸ =H or CH₃ and w=1,2,3,or 4; and more specifically the compounds having the following formulas(with tBu=tert. butyl):

    ((tBu--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S

    ((tBu--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S.sub.2

    ((tBu--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S.sub.3

    ((tBu--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S

    ((tBu--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S.sub.2

    ((tBu--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S.sub.3.

Processes for the preparation of the phosphosulphur compounds accordingto the invention are illustrated in the examples. More particularly dueto their good antioxidant, anticorrosive and in particular antiwear andextreme-pressure properties, each phosphosulphur compound according tothe invention can advantageously be used as an additive for inparticular mineral and/or synthetic lubricating oils at a concentrationof 0.05 to 5% by weight.

Therefore the present invention relates to a lubricating compositionincorporating a major proportion of lubricating oil and 0.05 to 5% byweight of at least one phosphosulphur compound according to theinvention.

The following examples illustrate the invention without limiting itsscope.

EXAMPLE 1 Synthesis of a Monosulphurized Dialkyldithiophosphoric Acid(Known Product)

In a first stage, 3000 cm³ of pure ethyl alcohol are introduced into a6000 cm³ three-necked reactor, followed by 372 g (9.3 mole) of sodiumhydroxide. After dissolving, the mixture is heated to 50° C. andprogressive addition takes place of 837.6 g (9.3 mole) of2-methyl-propane-2-thiol. At the end of addition, the temperature iskept at 50° C. for a further 30 minutes, followed by cooling to 20° C.This is followed by the progressive introduction of 878.8 g (9.3 mole)of n-chloropropanol. The mixture is brought to the reflux of the alcoholfor 6 hours and then cooled to ambient temperature.

The NaCl formed is eliminated by filtration and the organic solutionacidified by a 2N HCl aqueous solution. The organic phase is collectedand then the aqueous phase extracted by dichloromethane. The organicfractions are combined, washed with water, dried on anhydrous Na₂ SO₄and the dichloromethane is eliminated by evaporation under reducedpressure.

The product is purified by distillation under reduced pressure (PE=84°C./1 mnbar), which makes it possible to obtain 1370 g of a colourlessproduct with the following elementary analysis:

    ______________________________________                                        wt. % C         wt % H          wt. % S                                       Found Theory    Found   Theory  Found Theory                                  (Fd)  (Th)      (Fd)    (Th)    (Fd)  (Th)                                    ______________________________________                                        56.81 56.73     10.79   10.81   21.84 21.66                                   ______________________________________                                    

The expected chemical structure is confirmed by ¹³ C NMR analysis,namely:

    (CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --OH (monosulphurized alcohol).

In a second stage 189.6 g (1.28 mole) of previously preparedmonosulphurized alcohol and 400 cm³ chloroform are introduced into a2000 cm³ three-necked reactor. The mixture is heated to 60° C., followedby the progressive addition of 71.12 g (0.32 mole) of P₂ S₅. Aftercompletely dissolving the P₂ S₅, the mixture is kept for an additionalhour at 60° C. and accompanied by stirring. After eliminating thechloroform under reduced pressure, 240 g of a pale yellow liquid arecollected, which has the following elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd.   Th.    Fd.      Th.  Fd.    Th.  Fd.    Th.                             ______________________________________                                        43.21 43.05  7.97     7.94 32.71  32.86 8.02  7.94                            ______________________________________                                    

¹³ C NMR analysis confirms the expected chemical structure, i.e.:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O).sub.2 P(S)--SH

EXAMPLE 2 Synthesis of a Monosulphurized Zinc Dialkyldithiophosphate(Known Product)

Part of the previously obtained sulphurized dialkythiophosphoric acid(30 g, i.e. 0.077 mole) is transformed into sodium salt by adding to it100 cm³ of an aqueous sodium solution (NaOH=3.2 g, i.e. 0.08 mole). Thissodium salt is purified by successive extractions with hexane and thenthe recovered purified aqueous solution is treated with a solution of12.66 g (0.045 mole) of 7H₂ O ZnSO₄ dissolved in 30 cm³ of water. Thesulphurized zinc dialkyldithiophosphate then precipitates immediately.The mixture is extracted with chloroform, the organic phase recovered isdried on anhydrous Na₂ SO₄ and then the solvent is eliminated byevaporating under reduced pressure. In this way 20.3 g of a viscousyellow liquid are collected, which is in accordance with the followingelementary analysis:

    ______________________________________                                        wt. % C wt. % H   wt. % S   wt. % P wt. % Zn                                  Fd.  Th.    Fd.    Th.  Fd.  Th.  Fd.  Th.  Fd.  Th.                          ______________________________________                                        40.11                                                                              39.81  7.26   7.11 30.69                                                                              30.40                                                                              7.24 7.35 7.82 7.75                         ______________________________________                                    

Moreover, the infrared, ³¹ P and ¹³ C NMR analyses confirm the expectedchemical structure of the zinc salt, i.e.:

    (((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S).sub.2 Zn

EXAMPLE 3 Synthesis of a Monosulphurized Dialkyldithiophosphoric Alcohol

Part of the sulphurized dialkyldithiophosphoric acid obtained in Example1 (60 g, i.e. 0.154 mole) is introduced into a 250 cm³ three-neckedreactor, followed by the progressive addition of 10 g (0.172 mole) ofepoxypropane, whilst not exceeding a reaction temperature of 30° C.After evaporating the excess epoxy propane under reduced pressure, 66 gof pale yellow liquid are recovered and the elementary analysis is asfollows:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd.   Th.    Fd.      Th.  Fd.    Th.  Fd.    Th.                             ______________________________________                                        45.75 45.51  8.57     8.26 29.12  28.61 6.92  6.92                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure, namely:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--OH

EXAMPLE 4 Synthesis of a Monosulphurized ZincDialkyldithiophosphyldithiophosphate

Into a 250 cm³ three-necked reactor equipped with a Dean-Starkseparator, are introduced 1.7 g (0.016 mole) of sodium carbonate and 100cm³ of benzene. The mixture is refluxed for 1 hour to make the mediumanhydrous, followed by the addition of 3.66 g (0.0165 mole) of P₂ S₅.This is followed by the progressive introduction of 29.6 g (0.066 mole)of monosulphurized dialkyldithiophosphoric alcohol prepared in Example3. The mixture is then refluxed and kept there for 3 hours.

This is followed by cooling to 50° C. and the addition of 20 cm³ ofethyl alcohol containing 0.4 g (0.01 mole) of sodium hydroxide. Reactionis allowed to take place for 1 hour. Filtration takes place to eliminatethe P₂ S₅ in excess. This is followed by the addition of 50 cm³ of anaqueous solution containing 10 g of 7H₂ O ZnSO₄ (0.0356 mole) andreaction is allowed to take place for 2 hours, accompanied by vigorousstirring. This is followed by drying on Na₂ SO₄, filtering andevaporation of the benzene under reduced pressure. A pale viscous yellowliquid is recovered, which has the following elementary analysis:

    ______________________________________                                        wt. % C wt. % H   wt. % S   wt. % P wt. % Zn                                  Fd   Th     Fd     Th   Fd   Th   Fd   Th   Fd   Th                           ______________________________________                                        40.01                                                                              39.91  7.27   7.04 30.89                                                                              31.36                                                                              8.95 9.10 3.06 3.20                         ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure, namely:

    ((((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(S)--S--).sub.2 Zn

EXAMPLE 5 Synthesis of a Monosulphurized Dialkyldithiophosphoric AcidTriester

In a first stage, 30 g (0.2 mole) of monosulphurized alcohol prepared inExample 1 are dissolved in 60 cm³ of chloroform, followed by theprogressive addition of 11.9 g of SOCl₂ (0.1 mole). The mixture is thenrefluxed, followed by the progressive addition of 11.94 g of SOCl₂ (0.1mole), followed by the maintenance of reflux for a further 2 hours.After cooling, the chloroform is eliminated by evaporation and thechlorine derivative corresponding to the monosulphurized alcohol ispurified by distillation under reduced presdure (PE=92° C./1 mmbar),which gives 31.5 g of product (0.189 mole).

In a second stage, 27.3 g (0.07 mole) of monosulphurizeddialkyldithiophosphoric acid prepared in Example 1 are transformed intosodium salt in the manner indicated in Example 2. The aqueous purifiedsodium salt solution is then mixed with 1 g of tetrabutyl ammoniumhydrogen sulphate (phase transfer catalyst), followed by the addition of11.42 g (0.07 mole) of the halogen-containing derivative of thepreceding first stage dissolved in 10 cm³ of dichloromethane. Themixture is refluxed for 10 hours, cooled, the recovered organic phasewashed with water, dried on Na₂ SO₄, filtered and then evaporated underreduced pressure. In this way 35 g of product are recovered with thefollowing elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd.   Th.    Fd.      Th.  Fd.    Th.  Fd.    Th.                             ______________________________________                                        48.78 48.43  8.57     8.65 31.02  30.81 6.04  5.96                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure, namely:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--S--C--(CH.sub.3).sub.3

EXAMPLE 6 Synthesis of Monosulphurized Dialklychlorophosphates Example6.1 (known product)

Into a 500 cm³ three-necked reactor are introduced 16 g (0.104 mole) ofPOCl₃ dissolved in 50 cm³ of benzene. This is followed by the progessiveaddition of a solution constituted by 30.8 g (0.208 mole) ofmonosulphurized alcohol prepared in Example 1, 16 g of pyridine and 50cm³ of benzene. The mixture obtained is stirred at ambient temperaturefor one hour. The pyridinium chloride obtained is eliminated byfiltration, the organic phase washed with water, dried on Na₂ SO₄ andevaporated under reduced pressure. This gives 38 g of product with thefollowing elementary analysis:

    ______________________________________                                        wt. % C wt. % H   wt. % S   wt. % P wt. % Cl                                  Fd   Th     Fd     Th   Fd   Th   Fd   Th   Fd   Th                           ______________________________________                                        44.89                                                                              44.61  8.02   7.97 17.44                                                                              17.03                                                                              8.11 8.23 9.65 9.43                         ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(O)--Cl

Example 6.2: (novel product)

The same experiment performed on the basis of the monosulphurizedthiophosphorus alcohol prepared in Example 3 leads to a productcorresponding to the following formula:

    (((CH.sub.3).sub.3 C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(O)--Cl

EXAMPLE 7 Synthesis of Monosulphurized Zinc Dialkylphosphates Example7.1 (known product)

In a first stage vigorous stirring takes place of 18 g (0.048 mole) ofthe first monosulphurized dialkylchlorophosphate obtained in Example 6with 50 cm³ of an aqueous 2N sodium solution for 2 hours, followed bythe extraction of the mixture with toluene. The recovered aqueous phaseis acidified with 2N hydrochloric acid, extracted with toluene, washedwith water, dried on Na₂ SO₄, filtered and then evaporated under reducedpressure. This gives 15 g of a yellow liquid with the followingelementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        47.21 46.91  8.87     8.66 17.45  17.91 8.44  8.66                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the chemical structureof the expected monosulphurized dialkylphosphoric acid, namely:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(O)--OH

In a second stage neutralization takes place of 15 g (0.042 mole) ofmonosulphurized dialkylphosphoric acid prepared in the preceding firststage with 2.35 g of potassium dissolved in 50 cm³ of methyl alcohol.Stirring is maintained for 30 minutes at ambient temperature, followedby the addition of 12.7 g (0.045 mole) of 7H₂ O ZnSO₄ dissolved in 25cm³ of water. The mixture is stirred for 30 minutes at ambienttemperature, followed by extraction with ethyl alcohol. The recoveredorganic phase is washed with water, dried on Na₂ SO₄, filtered and thenevaporated under reduced pressure. This gives 15 g of a very viscous,opalescent liquid with the following elementary analysis:

    ______________________________________                                        wt. % C wt. % H   wt. % S   wt. % P wt. % Zn                                  Fd   Th     Fd     Th   Fd   Th   Fd   Th   Fd   Th                           ______________________________________                                        43.52                                                                              43.10  7.55   7.70 16.26                                                                              16.45                                                                              8.14 7.95 8.11 8.39                         ______________________________________                                    

The infrared, ³¹ P and ⁻⁻ C NMR analyses confirm the expected chemicalstructure, namely:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(O)--)--).sub.2 Zn

Example 7.2 (novel product)

The same experiment carried out on the basis of the chlorine derivativeof the monosulphurized thiophosphorus alcohol prepared in Example 3 (cf.Example 6.1) leads to a product corresponding to the following formula:

    ((((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(O)--O--).sub.2 Zn

EXAMPLE 8 Synthesis of Monosulphurized Trialkylphosphates Example 8.1(Known Product)

10 g (0.065 mole) of POCl₃ are dissolved in 50 cm³ of benzene. Themixture is cooled to 5° C., followed by the progressive addition of asolution of 28.9 g (0.195 mole) of the monosulphurized alcohol preparedin Example 1, 30 g of puridine and 50 cm³ of benzene, whilst maintainingthe reaction temperature at 5° C. Following addition, this temperatureis maintained for a further 30 minutes. This is followed by heating tothe reflux of the solvent and boiling is maintained for 2 hours. Thesolution is cooled, filtered, the organic phase washed water, dried onNa₂ SO₄, filtered and evaporated under reduced pressure. This gives 27 gof product with the following elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        51.87 51.62  9.54     9.22 19.22  19.70 6.11  6.35                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure, namely:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.3 P(O)

Example 8.2

The same experiment performed on the basis of the monosulphurizedthiophosphorus alcohol prepared in Example 3 leads to a productcorresponding to the following formula:

    (((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.3 P(O)

EXAMPLE 9 Synthesis of Monosulphurized Trialkylthiophosphates Example9.1

The experiment of Example 8.1 is repeated substituting the POCl₃ by thesame molar quantity of PSCl₃. After reaction and treatments, 24 g ofproduct are collected with the following elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        50.12 49.97  9.01     8.92 25.12  25.43 6.11  6.15                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure, namely:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.3 P(S)

Example 9.2

The same experiment performed on the basis of the monosulphurizedthiophosphorus alcohol prepared in Example 3 leads to a productcorresponding to the following formula:

    (((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.3 P(S)

EXAMPLE 10 Synthesis of Monosulphurized Dialkylphosphonates Example 10.1

30 g (0.18 mole) of monosulphurized alcohol prepared in Example 1 aredissolved in 100 cm³ of carbon tetrachloride. Then, at ambienttemperature, progressive addition takes place of 8.25 g (0.06 mole) ofPCl₃ dissolved in 50 cm³ of carbon tetrachloride. Boiling takes placeand this temperature is maintained for 1 hour. The solvent is eliminatedby evaporating under reduced pressure and the dialkylphosphonate isseparated from the halogen-containing derivative by liquid silica columnchromatography. This gives 18 g of product with the following elementaryanalysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        49.32 49.08  9.21     9.06 18.62  18.74 8.95  9.06                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure, namely:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(O)--H

Example 10.2

The same experiment, carried out on the basis of the monosulphurizedthiophosphorus alcohol prepared in Example 3, leads to a productcorresponding to the following formula:

    (((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(O)--H

These experiments (or syntheses) can be repeated using polysulphurizedalcohols (x>1). In this way it is possible to regulate at random thesulphur quantity contained in the additives according to the inventionand therefore obtain products having regulatable antiwear andextreme-pressure properties. The following examples illustrate thesepossibilities.

EXAMPLE 11 Synthesis of a Polysulphurized Alcohol

Into a 500 cm³ three-necked reactor are introduced 200 cm³ of methylalcohol and then 44 g (1.1 mole) of sodium hydroxide. After dissolving,the mixture is heated to 50° C., followed by the progressive addition of99 g (1.1 mole) of 2-methyl-2-propane-thiol. At the end of addition, thetemperature is maintained at 50° C. for a further 30 minutes. This isfollowed by the progressive addition of 33.2 g (1.1 gramme atom) ofelementary sulphur, then reaction is allowed to take place at 50° C.until the sulphur is completely dissolved. This is followed by theprogressive introduction of 92.5 g (1 mole) of n-chloropropanol. Themixture is heated to the reflux of the alcohol for 6 hours and thencooled to ambient temperature.

The NaCl formed is eliminated by filtration and the organic solutionevaporated under reduced pressure. The organic phase is washed withwater to eliminate the toluene-extracted sodium polysulphide excess,dried on Na₂ SO₄ and evaporated under reduced pressure. The crudepolysulphurized alcohol obtained is purified by liquid chromatography onsilica, whilst eluting the impurities with hexane (tert. butylpolysulphides), the desired product then being recovered by eluting withmethyl alcohol. After evaporating the methyl alcohol, in this way 173 gof polysulphurized tert. butyl alcohol are recovered with the followingelementary analysis:

    ______________________________________                                        wt. % C           wt. % H         wt. % S                                     Fd     Th         Fd     Th       Fd   Th                                     ______________________________________                                        46.87  46.63      8.92   8.88     35.24                                                                              35.60                                  ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure, namely a statistical mixture of sulphurized alcohols of thefollowing summary formula:

    (CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --OH

EXAMPLE 12 Synthesis of a Polysulphurized Dialkyldithiophosphoric Acid

Into a 1000 cm³ three-necked reactor are introduced 150 g (0.83 mole) ofpolysulphurized alcohol prepared in Example 11 and 400 cm³ ofchloroform. The mixture is heated to 60° C., followed by the progressiveaddition of 46.11 g (0.207 mole) of P₂ S₅. After complete dissolving ofthe P₂ S₅, the mixture is kept for an additional hour at 60° C.,accompanied by stirring. After eliminating the chloroform under reducedpressure, 185 g of pale yellow liquid are collected with the followingelementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        37.12 36.97  6.92     6.82 42.11  42.34                                                                              6.71   6.82                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure, namely:

    ((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--SH

EXAMPLE 13 Synthesis of a Polysulphurized DialkyldithiophosphoricAlcohol

100 g of polysulphurized dialkyldithiophosphoric acid obtained inExample 12 (0.22 mole) are introduced into a 500 cm³ three-neckedreactor, followed by the progressive addition of 15 g (0.26 mole) ofepoxy propane, whilst not exceeding a reaction temperature of 30° C.After reducing the excess epoxy propane under reduced pressure, 112 g ofpale yellow liquid are recovered with the following elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        39.94 39.81  7.35     7.22 37.32  37.55                                                                              6.01   6.05                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure of the alcohol, namely:

    ((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2)--CH(CH.sub.3)--OH

EXAMPLE 14 Synthesis of Polysulphurized Zinc Dialkyldithiophosphate

The experiments of Examples 1 and 2 are repeated with thepolysulphurized alcohol prepared in Example 11. Following the reactionsand separation, a polysulphurized zinc dialkyldithiophosphate with thefollowing elementary analysis is obtained:

    ______________________________________                                        wt. % C wt. % H   wt. % S   wt. % P wt. % Zn                                  Fd   Th     Fd     Th   Fd   Th   Fd   Th   Fd   Th                           ______________________________________                                        34.82                                                                              34.56  6.37   6.17 39.21                                                                              39.58                                                                              6.14 6.38 6.46 6.73                         ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the expected chemicalstructure of the product, namely:

    (((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S).sub.2 Zn

EXAMPLE 15 Synthesis of a Polysulphurized Zinc DialkyldithiophosphylDithiophosphate

The experiment of Example 4 is repeated with the polysulphurizeddialkyldithiophosphoric alcohol prepared in Example 13. Followingreactions and separation, a polysulphurized zinc dialkyldithiophosphyldithiophosphate is obtained with the following elementary analysis:

    ______________________________________                                        wt. % C wt. % H   wt. % S   wt. % P wt. % Zn                                  Fd   Th     Fd     Th   Fd   Th   Fd   Th   Fd   Th                           ______________________________________                                        35.58                                                                              35.46  6.46   6.26 38.67                                                                              39.01                                                                              7.95 8.08 2.64 2.84                         ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses confirm the chemical structureof the product, namely:

    ((((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(S)--S--).sub.2 Zn

Evaluation of the Extreme-pressure and Antiwear Properties of theAdditives According to the Invention

Tests are carried out to reveal the antiwear and extreme-pressureproperties of the additives according to the invention in lubricatingformulations of the gear oil type.

The additives of Examples 2,3,4,5,8.1,9.1,10.1,11,14 and 15 were studiedwith the aid of a machine with four balls according to the procedure ofASTM D 2783 at concentrations such that the sulphur content of themineral-based oil SAE 80W90 is equal to or close to 0.2% by weight. Theresults obtained are given in Table 1.

It can in particular be seen that the functional additives according tothe invention have good antiwear and extreme-pressure properties, whichcan be modified as a function of the sulphur quantity used in thesyntheses. It can also be seen that for the same sulphur concentrationthe polysulphide-type additives (in this case x=2) generally have betterperformance characteristics than the monosulphide-type additives (x=1),which gives the possibility of regulating at random the mechanicalperformance characteristics of these products, as a function of thevalue chosen for x (1,2,3 etc). This improvement can be advantageouslyused in the formulation of lubricating oils, especially for gears.

                                      TABLE 1                                     __________________________________________________________________________                                                 Wear                                         Additive   Extreme-Pressure      Impression diameter (mm)         S quantity  quantity                                                                           S quantity                                                                          Wear load                                                                            Load before    1 h under load of                Additive                                                                            in additive                                                                         in oil                                                                             in oil                                                                              value  seizing Welding load                                                                         40 kgf                                                                              60 kgf                                                                              80 kgf               of Example                                                                          wt. % wt. %                                                                              wt. % kgf                                                                              Newt                                                                              kgf                                                                              Newt kgf                                                                              Newt                                                                              392.4 Newt                                                                          588.6                                                                               784.8                __________________________________________________________________________                                                             Newt                 --    --    --   --    28.0                                                                             274.7                                                                             50 490.5                                                                              150                                                                              1471.5                                                                            1.47  1.90  2.50                 2     30.69 0.652                                                                              0.2   36.0                                                                             353.2                                                                             80 784.8                                                                              200                                                                              1962.0                                                                            0.36  0.68  0.98                 14    39.21 0.510                                                                              0.2   55.4                                                                             543.5                                                                             126                                                                              1236.1                                                                             250                                                                              2452.5                                                                            0.33  0.60  0.87                 4     30.89 0.647                                                                              0.2   42.9                                                                             420.8                                                                             100                                                                              981.0                                                                              200                                                                              1962.0                                                                            0.45  0.66  0.98                 15    38.67 0.517                                                                              0.2   47.0                                                                             461.1                                                                             100                                                                              981.0                                                                              250                                                                              2452.5                                                                            0.37  0.65  0.90                 3     29.12 0.755                                                                              0.22  34.9                                                                             342.4                                                                             80 784.8                                                                              200                                                                              1962.0                                                                            0.35  0.52  1.10                 5     31.02 0.709                                                                              0.22  33.8                                                                             331.6                                                                             80 784.8                                                                              200                                                                              1962.0                                                                            0.36  0.55  1.07                 8.1   19.22 1.116                                                                              0.22  35.9                                                                             352.2                                                                             80 784.8                                                                              200                                                                              1962.0                                                                            0.39  0.67  0.93                 9.1   25.12 0.875                                                                              0.22  42.9                                                                             420.8                                                                             100                                                                              981.0                                                                              250                                                                              2452.5                                                                            0.37  0;61  0.90                 10.1  18.62 1.182                                                                              0.22  50.6                                                                             496.4                                                                             126                                                                              1236.1                                                                             200                                                                              1962.0                                                                            0.42  0.48  1.20                 11    35.24 0.624                                                                              0.22  37.2                                                                             364.9                                                                             80 784.8                                                                              200                                                                              1962.0                                                                            0.39  0.54  1.09                 __________________________________________________________________________

EXAMPLE 16 Synthesis of the Compound

    (((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S

a. First stage, preparation of the monosulphurized alcohol:

    (CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --OH

150 cm³ of pure ethyl alcohol are introduced into a 500 cm³ three-neckedreactor, followed by 18.6 g (0.465 g-mole) of sodium hydroxide. Afterdissolving, the mixture is heated to 50° C., followed by the progressiveaddition of 41.9 g (0.465 g-mole) of 2-methyl-2-propane thiol. At theend of addition, the temperature is kept at 50° C. for a further 30minutes, followed by cooling to 20° C. This is followed by theprogressive addition of 43.95 g (0.465 g-mole) of n-chloropropanol, themixture then being heated to the reflux of alcohol for 6 hours, followedby cooling to ambient temperature.

The NaCl formed is eliminated by filtration and the organic solutionacidified by a 2N HCl aqueous solution. The organic phase is collectedand then the aqueous phase extracted by dichloromethane. The organicfractions are combined, washed with water, dried on anhydrous Na₂ SO₄and the dichloromethane is eliminated by evaporation under reducedpressure.

The purification of the sulphur-containing alcohol takes place bydistillation under reduced pressure (PE=84° C./1 mbar). 68.5 g ofcolourless product are recovered with the following elementary analysis:

    ______________________________________                                        wt. % C           wt. % H         wt. % S                                     Fd     Th         Fd     Th       Fd   Th                                     ______________________________________                                        56.81  56.73      10.79  10.81    21.84                                                                              21.66                                  ______________________________________                                    

The infrared, ¹ H and ¹³ C NMR analyses confirm the chemical structureof the product.

b. Second stage, preparation of a monosulphurizeddialkyldithiophosphoric acid:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--SH

Into a 250 cm³ reactor are introduced 19.0 g (0.128 g-mole) ofmonosulphurized alcohol prepared in the first stage and 40 cm³ ofchloroform. The mixture is heated to 60° C., followed by the progressiveaddition of 7.11 g (0.032 g-mole) of P₂ S₅. After complete dissolving,the mixture is kept for an additional hour at 60° C. and accompanied bystirring. After eliminating the chloroform under reduced pressure, 24 gof a pale yellow liquid are obtained with the following elementaryanalysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        43.21 43.05  7.97     7.94 32.71  32.86                                                                              8.02   7.94                            ______________________________________                                    

The infrared, ¹ H and ¹³ C analyses confirm the expected chemicalstructure of the product.

c. Third stage, preparation of a monosulphurized dialkyldithiophosphoricalcohol:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --OH

Into a 100 cm³ reactor are introduced 22.0 g (0.0564 g-mole) ofsulphur-containing dialkyldithiophosphoric acid prepared in thepreceding stage, followed by the addition of 2.8 g (0.064 g-mole) ofethylene oxide, accompanied by stirring and whilst vigorously cooling inorder to maintain a temperature of 25° C. The ethylene oxide excess iseliminated by evaporation under reduced pressure and 24 g of a viscousliquid are collected having the following elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        44.09 44.22  8.12     8.06 29.32  29.53                                                                              7.03   7.14                            ______________________________________                                    

The infrared, ¹ H, ³¹ P and ¹³ C NMR analyses confirm the expectedchemical structure of the product.

Fourth stage, preparation of the chloride corresponding to the precedingmonosulphurized dialkyldithiophosphoric alcohol:

    ((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --Cl

Into a 100 cm³ reactor are introduced 20.0 g (0.046 g-mole) ofmonosulphurized dialkyldithiophosphoric alcohol prepared in thepreceding stage, followed by the addition of 20 g of chloroform and thenvery progressively 2.74 g (0.023 g-mole) of SOCl₂, whilst maintainingthe reaction temperature at about 20° C. The mixture is then refluxedand then very progressive addition again takes place of the same SOCl₂quantity. After cooling, the chloroform is eliminated under reducedpressure in order to collect approximately 20 g of product, whoseinfrared, ³¹ P, ¹ H and ¹³ C NMR analyses correspond to the expectedchemical structure of the product.

Fifth and final stage, preparation of the sought compound:

    (((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S

Into the reactor of the preceding stage are introduced 20 g ofchloroform in order to dissolve the chlorine-containing derivativefollowed by 1 g of tetrabutyl ammonium chloride (phase transfercatalyst) and finally very progressive 20 cm³ of an aqueous solutioncontaining 7 g of 9H₂ O Na₂ S (0.03 g-mole) whilst maintaining thetemperature at about 20° C. The mixture is then refluxed for 1 hour,cooled and the phases separated. The recovered organic fraction iswashed with water, dried on anhydrous NaSO₄ and then filtered to collect19 g of product with the following elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        44.89 44.31  7.99     7.85 32.47  33.30                                                                              7.01   7.15                            ______________________________________                                    

The infrared, ¹ H, ³¹ P and ¹³ C NMR analyses confirm the chemicalstructure of the product.

EXAMPLE 17 Synthesis of the Compound

    (((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S

The first stage (a) of Example 16 is repeated, whilst adding to thereaction mixture 14.91 g (0.465 g-mole) of elementary sulphur in orderto statistically form the disulphurized compound. After reaction, thecrude disulphurized alcohol obtained is purified by liquidchromatography on silica gel, followed by elution with hexane in orderto eliminate the impurities and with methyl alcohol which, afterevaporation under reduced pressure, makes possible to recover the soughtpurified, disulphurized alcohol. The experiment is continued using thesame molar proportions of reagents in order to obtain after the fifthstage (e) a product with the following elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        38.97 38.60  7.05     6.84 41.02  41.90                                                                              6.01   6.23                            ______________________________________                                    

The infrared, ³¹ P and ¹³ C NMR analyses correspond to the expectedchemical structure of the product.

EXAMPLE 18 Synthesis of the Compound

    (((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S.sub.2

The experiment of Example 16 is integrally repeated up to the fifthstage, where use is made of 25 cm³ of an aqueous solution containing 7 gof 9H₂ O Na₂ S (0.03 g-mole) and 1 g of elementary sulphur (0.03 g-atom)for statistically forming the disulphurized compound. This gives aproduct with the following elementary analysis:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        43.22 42.73  7.85     7.57 34.89  35.68                                                                              6.73   6.90                            ______________________________________                                    

The infrared, ³¹ P, ¹ H and ¹³ C NMR analyses correspond to the chemicalstructure of the statistically expected product.

EXAMPLE 19 Synthesis of the Compound

    (((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S.sub.3

The experiment of Example 17 is repeated in order to prepare thesulphur-containing disulphurized dialkyldithiophosphorus alcohol. Theexperiment is continued, all molar proportions between the reagentsbeing maintained, up to the fifth stage where use is made of 25 cm³ ofan aqueous solution constituted by 7 g of 9H₂ O Na₂ S (0.03 g-mole) and2 g of elementary sulphur (0.06 g-atom) in order to form thestatistically sought trisulphurized compound. A product with thefollowing elementary analysis is obtained:

    ______________________________________                                        wt. % C       wt. % H       wt. % S     wt. % P                               Fd    Th     Fd       Th   Fd     Th   Fd     Th                              ______________________________________                                        36.86 36.26  6.78     6.42 44.71  45.42                                                                              5.34   5.85                            ______________________________________                                    

The infrared, ³¹ P, ¹ H and ¹³ C NMR analyses correspond to the chemicalstructure of the statistically expected product.

Evaluation of the Extreme-pressure and Antiwear Properties of theAdditives of Examples 16 to 19

Tests are carried out to reveal the extreme-pressure and antiwearproperties of the additives according to the invention using a machinewith four balls according to the procedure of ASTM D 2783, underconcentrations such that the sulphur content of the mineral oil SAE80W90 is equal to 0.22% by weight. The results obtained are given inTable 2.

These results show that the additives according to the invention havegood antiwear and extreme-pressure properties and that these can bemodified as a function of the elementary sulphur quantity used in thesyntheses. It is in particular shown that for an equal sulphurconcentration, the compounds having polysulphide units are moreeffective than those having monosulphide units, which gives apossibility of regulating at random the mechanical performancecharacteristics of these products. This improvement can be used withadvantage in the formulation of lubricating oils for gears or for theworking of metals.

                                      TABLE 1                                     __________________________________________________________________________                                                 Wear                                         Additive   Extreme-Pressure      Impression diameter (mm)         S quantity  quantity                                                                           S quantity                                                                          Wear load                                                                            Load before    1 h under load of                Additive                                                                            in additive                                                                         in oil                                                                             in oil                                                                              value  welding Welding load                                                                         40 kgf                                                                              60 kgf                                                                              80 kgf               of Example                                                                          wt. % wt. %                                                                              wt. % kgf                                                                              Newt                                                                              kgf                                                                              Newt kgf                                                                              Newt                                                                              392.4 Newt                                                                          588.6                                                                               784.8                __________________________________________________________________________                                                             Newt                 --    --    0    --    28.0                                                                             274.7                                                                             50 490.5                                                                              150                                                                              1471.5                                                                            1.47  1.90  2.50                 16    32.47 0.68 0.22  33.8                                                                             331.6                                                                             80 784.8                                                                              200                                                                              1962.0                                                                            0.40  0.58  1.07                 17    41.02 0.54 0.22  43&0                                                                             421.8                                                                             100                                                                              981.0                                                                              200                                                                              1962.0                                                                            0.39  0.55  0.98                 18    34.89 0.63 0.22  36.0                                                                             353.2                                                                             80 784.8                                                                              200                                                                              1962.0                                                                            0.39  0.65  0.95                 19    44.71 0.49 0.22  55.1                                                                             540.5                                                                             126                                                                              1236.1                                                                             250                                                                              2452.5                                                                            0.35  0.60  0.89                 __________________________________________________________________________

We claim:
 1. A process for preparing an alcohol of the formula

    R.sup.1 --Sx--(CH.sub.2).sub.n --OH

wherein R¹ is an alkyl or alkenyl group with 4 carbon atoms, x is 2, 3or 4, and n is at least 3,comprising reacting a R¹ --SH thiol with ahaloalkanol of the formula

    Hal--(CH.sub.2).sub.n OH,

in which Hal is a halogen atom, with the addition of elemental sulfur,in the presence of alkali and in an alcoholic medium.
 2. A processaccording to claim 1, wherein x is 2 and n is
 3. 3. A process accordingto claim 1, comprising reacting 2-methyl-propane-2-thiol-with elementalsulfur and with 3-chloropropanol, to produce (CH₃)₃ C--S₂ --(CH₂)₃ --OH.4. A process according to claim 1, wherein R¹ is tert-butyl ormethallyl, x is 2, 3 or 4 and n is 3 or
 4. 5. A process according toclaim 4, wherein x=2 and n=3.